Rocket propulsion method



Dec. 18 1956 F. J. MALINA ETA ROCKET PROPULSION METHOD Original FiledMay 8, 1945 OXIDIZER FUEL INERT GAS IN VEN TOR. JOHN A. PARSONS FRANK J.MALI/VA ATTORNEY ROCKET PROPULSION IVIETHOD Frank J. Malina and John W.Parsons, Pasadena, assignors to Aerojet-General Corporation, Cincinnati,

Ohio, a corporation of Ohio Application September 1, 1950, Serial No.182,742, which is a division of application Serial No. 486,236, May 8,1943, now Patent No. 2,573,471, dated October 30, 1951. Divided and thisapplication February 8, 1954, Serial No. 412,196

3 Claims. (Cl. 60-354) Our invention relates to jet propulsion and moreparticularly to propellants which are useful in connection therewith.This is a division of my copending application Serial No. 182,742, filedSeptember 1, 1950, now Patent No. 2,693,077 issued November 2, 1954, asa division of application Serial No. 486,236, filed May 8, 1943, nowPatent No. 2,573,471, issued October 30, 1951.

While our invention is capable of use in connection with the propulsionof a wide variety of different devices and vehicles, since it findsparticular utility in the propulsion of aircraft, its advantages aredescribed with relation to such use, it being understood that ourinvention is, however, not limited to such use.

Prior to our invention special means were always required to ignite thepropellants. For example, when liquid oxygen is used as an oxidizer andgasoline is used as a fuel, some auxiliary ignition means must always beprovided to initiate combustion of the propellants.

This is objectionable because it requires either a spark plug or otherignitor or means for heating the Walls of the combustion chamber abovethe ignition point of the propellant mixture making this system complexand dependent upon the operation of such ignition system.

While spontaneous combustion is obtained with our preferred combinationsof propellants which is especially effective when operating inaccordance with our preferred method it will be understood that thepropellants we have discovered offer advantages even when operatingunder other conditions.

The present invention relates to fuels, and oxidizers and theircombination as propellants and their method of injection into a jetmotor. Among the objects of our invention are: to provide more eflicientand effective propellants for jet propulsion systems; to provide anoxidizing agent which is easily combustible with a suitable fuel andwhich has a large amount of oxygen available for burning a fuel; toprovide propellants, that is, fuels and oxidizers, which arespontaneously combustible; to provide a method for utilizing suchpropellants to give smooth combustion and to eliminate danger ofexplosion; to obviate the difiiculties attendant upon the use ofliquified gases; to eliminate the need of an auxiliary ignition systemto ignite the propellants.

Oxidizers As a result of a thorough investigation of the variousoxidizing agents which may be used as propellants we prefer to employnitric acid. Since water tends to retard combustion of the acid with anyfuel, the nitric acid should be substantially free of water. Thus, whitefuming nitric acid, which normally contains less than about 2% of waterby weight, is to be preferred to weaker solutions of nitric acid.However, we have found that more dilute solutions of nitric acid may beutilized provided that nitrogen dioxide is dissolved in the nitric acid;which is a way of increasing the concentration of an otherwise moredilute solution. Prefer- Patented Dec. 18, 1956 ably the nitric acidshould contain at least about 5% N02 but preferably at least about 15 to20% N02. Such a solution of nitrogen dioxide is known as red fumingnitric acid and almost all red fuming nitric acid which is commerciallyavailable in this country contains between about 5% and 20% nitrogendioxide by weight and less than about 5% water by weight. Specificationsfor nitric acid, obtainable commercially as red fuming nitric acid, areas follows:

Chemical composition:

Specifications for nitric acid, obtainable commercially as white fumingnitric acid, are as follows:

Chemical composition:

Nitric acid 97.5% by wt. min. Water 2.0% by wt. max. N02 content 0.5% bywt. max. Physical properties: Density 1.46 min-41.52 max. at

68 F. Melting point -45 F. Color, etc Straw yellow to water white;

fumes vigorously when exposed to air.

The term white fuming nitric acid as used herein means a nitric acidcontaining a maximum of about 2% water by weight.

The term red fuming nitric acid as used herein means a nitric acidcontaining at least about 5% N02 and a maximum of about 5% water, byweight.

Nitric acid of all types containing at least HNOs is useful as anoxidizer. We have also found that liquid nitrogen dioxide is a verysatisfactory oxidizer.

To eliminate the requirement for providing the jet motor with specialigniting means, we employ nitric acid, and preferably red 'fuming nitricacid, substantially free of water, as an oxidizer.

Fuels We have discovered a family of fuels which are spontaneous'lycombustible with the oxidizing agents hereinabove mentioned and whichare satisfactory for jet propulsion provided that the propellants aresupplied to the combustion chamber under suitable operating conditions.These operating conditions are discussed more in detail hereinbelow.

We have found that the four groups of compounds listed below may beutilized as fuels. These groups are listed in the order of theirefiectiveness.

Group I.Liquid organic compounds containing at least one amine radical,such as,

A. Aniline, orthotoluidine, and methylamine.

B. Liquid hydrocarbons, containing large percentages of such aminesubstituted organic compounds.

Group II.Highly unsaturated hydrocarbons: Liquid hydrocarbons of theacetylene type and containing a large fraction of unsaturated (doubleand triple) carbon bonds, or both, for example, divinyl acetylene,dipropargyl, and prop-argyl alcohol. 7

Group III.-Liquidsubstances containing the elements having theproperties of lithium (Li), beryllium (Be), boron (B), aluminum (A1),magnesium (Mg), phosphorus (P), potassium ('K), and. sodium (Na). Withthe exception of phosphorus all of the foregoing elements. are.particularly useful in fuels because they generate large amounts of heatduring combustion, and phosphorus is particularly useful because it hasa low ignition temperature.

A. Liquid hydrides of those elements.

B. Liquid organo-metallic compounds containing one or more of suchelements.

C. Liquid fuels containing one or more such. elements.

D. Liquid fuels containing one or more such elemerits in suspension.

Group IV.-Organic compounds having the properties of -While aniline istoxic it has the great advantage of being relatively inexpensive, eventhough more expensive than gasoline, and of being commercially availablein large quantities.

Method of operation The above mentioned oxidizers and fuels may be usedi together as pairs of spontaneously combustible propellantszit-atmospheric temperature and pressure. However, if desired theseoxidizers and fuels may be used with other fuels (such as gasoline) orother oxidizers (such as liquid oxygen) respectively.

So far as we know we are the first to achieve spontaneous combustion injet propulsion systems at the temperature and pressure of the mediumsurrounding the jet motor and while other fuels and oxidizers might beutilized to accomplish such spontaneous combustion we prefer to use the[fuels and oxidizers hereinbefore mentioned.

Certain difficulties are encountered when utilizing these propellantsfor propulsion. Unless the propellants are supplied to the jet motorunder the proper conditions the motor is liable to fail completely, topulsate in its operation, or to explode, even though the propellants aresupplied at uniform rates.

These difliculties may be eliminated and certainty and smoothnes ofoperation secured by so relating the rates of injection of fuel andoxidizer to the size of the jet chamber and the inherent ignitionproperties of the mixture that explosion of the combustible mixture isavoided during the initial combustion, and subsequent inject-ion occursat rates conducive to the combustion of the continuously suppliedpropellants so as to avoid the accumulation in the jet chamber of anysubstantial amount of the unburned propellants. To achieve this result,we initially inject propellants into the combustion chamber at ratessuch that the amount of propellants injected prior to the initiation ofcombustion is lessthan about 20% of the volume of the combustionchamber. After combustion has been initiated, the propellants may beinjected at a greater rate than they are injected initially inasmuch asthe time interval between their 5 injection and combustion is reducedbecause of the higher temperature and pressure of the mixture resultingThe fuels and oxidizers hereinbefore described are advantageouslyemployed in the propulsion of an aircraft by providing the fuel andoxidizer in separate-containers 11 and 12 respectively connected in anysuitable manner as by pipes 13 and 14 to a jet or combustion Throttlevalves 16 and 17 energized by elec chamber. trical circuits 18 and 19are provided in said pipes to control the rates of supply of the fueland oxidizer re- 7 20 spectively to the combustion chamber 15. Areceptacle 20 is connected by a conduit 21 having a pressure regulator22 therein to the receptacles 11 and 12 and is provided with a gas underpressure, preferably a gas inert with respect to either propellant.Preferably the 25 container for the fuel and the container for theoxidizer.

are connected to a source of pressure adapted to force the contents ofsuch-containers into the jet or combustion chamber at controlled ratesdetermined by the degree of opening of the valves in said pipes.

plates so relating the rates of'injection of the oxidizer and of thefuel'to the combustion or jet chamber to theirinherent combustionproperties and the size and temperature of the chamber that smoothnon-explosive combustion occurs initially and throughout the entireoperation while providing the desired quantity of propulsive power.

when the combustion chamber is initially at atmospheric temperature, orat the temperature of any other medium 40 in which the motor is tooperate, as we are able to achieve combustion initially withoutauxiliary ignition or preheating of the chamber or the propellants.

If the propellants are supplied at such initial rates,

then, when the propellants are initially injected into the jet motor,the initially burned propellants soon fil-l the .combustion chamber withhigh temperature gases and vapors which heat the incoming propellantsthereby vaporizing them and reducing the ignition time lag.

Then the subsequently injected propellants burn spontaneously withoutany substantial accumulation of propellants in the liquid phase.

As an example, applied to a combustion chamber having a length of about10 inches and a cross sectional area of about 7 square inches, highlyconcentrated nitric add and aniline operate very satisfactorily whenthey are .injected into the'combustion chamber initially and prior tocombustion at the rates of 3.6 lbs. per second and 2.4

'lbs. per second respectively.

/ While these propellants and method of use and the apparatus for theiruse in propelling aircraft or other devices, which are hereinbeforedescribed, are fully capable of providing the advantages primarilystated, it will be recognized by those skilled in the art that variousmodifications and alterations may be made therein while still providingsuch advantages, and our invention is therefore tobe understood as notlimited to the specific i-embodiments hereinbefore described but asincluding all modifications. and variations thereof coming within thescope of the claims which follow.

We claim as our invention:

.1. The method of producing thrust which comprises ejecting, from .areaction chamber, the gaseous products produced by the spontaneouscombustion of an oxidizer selected from the group consisting of redfuming nitric 75" acid, white fuming nitric acid and nitrogen dioxide;and

The practice of the method of our invention contem- 7 Our invention isparticularly advantageous a heterocyclic nitrogen compound selected fromthe group consisting of pyrrole and pyridine.

2. The method of producing thrust which comprises ejecting, from areaction chamber, the gaseous products produced by the spontaneouscombustion of an oxidizer 5 References Cited in the file of this patentUNITED STATES PATENTS 1,506,323 ONeill Aug. 26, 1924 FOREIGN PATENTS476,227 Great Britain Dec. 3, 1937 OTHER REFERENCES Finnemore: EssentialOils, E. Benn Limited, London Hackhs Chemical Dictionary. Philadelphia,3rd ed., pp. 837, 876.

The Blakiston Co.,

1. THE METHOD OF PRODUCING THURST WHICH COMPRISES EJECTING, FROM AREACTION CHAMBER, THE GASEOUS PRODUCTS PRODUCED BY THE SPONTANEOUSCOMBUSTION OF AN OXIDIZER SELECTED FROM THE GROUP CONSISTING OF REDFUMING NITRIC ACID, WHITE FUMING NITRIC ACID AND NITROGEN DIOXIDE; AND